As larger amounts of memory are able to be stored in smaller spaces, users can store more data than ever before. Data can be graphically represented in a variety of ways, including by a chart. Many types of charts can be used to represent data, including bar charts, pie charts, and line charts. Line charts are similar to scatter plots, except that measurement points are ordered (typically by their X-axis value) and joined with straight line segments. Often times, line charts show how data changes over equal intervals of time. As such, the X-axis in a line chart can represent an hour, a day, a year, etc. Line charts are often used to visualize a trend in data over intervals of time, and thus the line is often drawn chronologically.
Comparing two line charts by their appearance can be difficult for many reasons. For instance, various line charts may display time in different intervals/resolutions. While the data displayed on two line charts may look the same, one chart may include data for a given day while another may include data for a given week. Similarly, the Y-axes on various charts have different minimum and/or maximum values. For instance, the Y-axes on two charts may both display temperature, but one chart may display up to 200 degrees, while the other chart only displays up to 100 degrees. Thus, although the scale of two line charts may be different, the data represented by the graphs may appear very similar when normalized.